4 June 2008 - Plastic plumbing systems, such as those made from PVC and cross-linked polyethylene, are more likely to deliver lead-laden drinking water than their copper counterparts.
This is according to a new study published in the peer-reviewed Environmental Science & Technology, which is a published by the American Chemical Society in Washington.
The findings initially seemed counter-intuitive, but researchers found that the metal present in plumbing systems was, ironically, causing the problem.
Professor Marc Edwards, one of the study’s lead researchers, told Plastics News: “Brass is ubiquitous in domestic plumbing systems.”
Edwards, a civil and environmental engineering expert based at the Virginia Tech University in Blacksburg, added: “It is an integral component in valves and faucets. Some of the brass has lead in it. In newer homes, brass is the primary source of lead in drinking water.”
Lead is not leaching from PVC or PEX. However, the plastic pipe does indirectly create an environment for lead to contaminate drinking water, the study found.
Water utility firms are increasingly treating water with chloramine to comply with disinfection regulations. Chloramine decay forms ammonia, which in turn supports “autotrophic microbial nitrification,” according to the study.
The nitrification process can stimulate growth of heterotrophic bacteria, all of which lowers acidity levels, and can result in quality degradation while water sits stagnant in plumbing pipes.
Edwards said: “To oversimplify, the nitrifying bacteria grew very easily in PVC pipe and did not grow in copper.”
He added: “As a result, the pH was about one unit lower in PVC pipes. It’s an indirect effect in that the presence of PVC allowed this bacteria to grow, which lowered the pH, which in turn caused the lead contamination.”
Kitchen and bathroom faucets are made mostly from brass and, Edwards argued, are “undoubtedly the major sources of the lead”.
He added that leaded brass can be found in PEX fittings, shut-off valves and water meters and while the findings are not cause for panic, they are cause for concern.
“It doesn’t pose nearly the hazard that lead paint, or lead in water from solder or lead pipe, causes,” Edwards said. “The levels we’re talking about do exceed [Environmental Protection Agency] recommendation.
“There is no safe level of lead exposure.”
Running water for 10-20 seconds before drinking is one way to effectively flush contaminated water from the system. Water filters are another safety method and retrofitting of brass faucets and parts is also an option, Edwards said.
“I’m not an advocate for any one type of plumbing material,” he said. “I’m a scientist. We were just trying to point out the strengths and weaknesses for each material in different situations. This explained some perplexing practical data that was out there.
“In general, each plumbing material has its strengths and weaknesses. Homeowners have to weigh those when making decisions.”
Matt Griswold is a journalist at Plastics News a sister title of PRW and EPN.
